(1) Field of the Invention
The present invention relates to an optical fiber array including a V-groove substrate having a V-groove on which an optical fiber is arranged and a fiber fix substrate for fixing the optical fiber arranged on the V-groove.
(2) Related Art Statement
Usually, as a member constructing a highly reliable optical connector, various types of optical fiber arrays, which include a V-groove substrate having a V-groove on which an optical fiber is arranged and a fiber fix substrate for fixing the optical fiber arranged on the V-groove, are known.
FIG. 8 is a schematic view showing one embodiment of a known optical fiber array. In FIG. 8, an optical fiber array 21 comprises a V-groove substrate 24 having a V-groove 23 on which an optical fiber 22 is arranged, and a fiber fix substrate 25 for fixing the optical fiber 22 arranged on the V-groove 23. The V-groove substrate 24 and the fiber fix substrate 25 are connected to each other at a fiber connecting plane 26 by using an adhesive and so on.
The V-groove 23 is arranged partly from one end along a longitudinal direction A of the optical fiber array 21. A concave portion not shown is arranged in the connected V-groove substrate 24 and the fiber fix substrate 25 from one end of the V-groove 23 to the other end of the optical fiber array. Therefore, a tape fiber 27, in which a predetermined number of the optical fibers 22, i.e., four optical fibers 22 in FIG. 8, are integrated, is fixed in the optical fiber array 21 in such a manner that bared optical fibers 22 at one end portion of the tape fiber 27 are fixed on the V-grooves 23 and the tape fiber 27 other than the bared optical fibers 22 is fixed in the concave portion mentioned above.
In the known optical fiber array 21 mentioned above, the V-groove substrate 24 and the fiber fix substrate 25 are connected at the fiber connecting plane 26 having a linear shape. Therefore, if heat and humidity are applied to the known optical fiber array 21, a water component is introduced along the fiber connecting plane 26 from the exposed end thereof, and the V-groove substrate 24 and the fiber fix substrate 25 are liable to be disconnected from each other. Therefore, it is necessary to use a special high reliability adhesive, and thus there is a large limitation on manufacturing the optical fiber array 21.
In order to eliminate the drawbacks mentioned above, as shown in Japanese Utility-model Laid-open Publication No. 4-101504, it is possible to use an optical fiber in which one of the V-groove substrate 24 and the fiber fix substrate 25 has a concave portion into which the other substrate is arranged in such a manner that a bottom surface of the concave portion of the one substrate is connected to a bottom surface of the other substrate directly or via the optical fiber 22. One example of such an embodiment is shown in FIG. 9 in which the V-groove substrate 24 has the concave portion having side end walls 28 whose thickness is thicker than that of a bottom portion 29 in which the V-grooves 23 are formed.
In the embodiment shown in FIG. 9, the V-groove substrate 24 and the fiber fix substrate 25 are connected by using an adhesive of an ultraviolet hardening type. Therefore, the following disadvantages occur.
(1) In FIG. 9, if an ultraviolet light (UV light) is incident upon the optical fiber array 21 from an upper side, the incident light is not introduced into all portion of an adhesive 31 arranged between an inner side surface of the V-groove substrate 24 which constructs the concave portion and an outer side surface of the fiber fix substrate 25 i.e., into a portion to which the bottom portion of the V-groove substrate 24 is contacted. In this case, a non-hardening portion of the adhesive 31 occurs as shown in FIG. 10a. Therefore, a reliability of the optical fiber array 21 becomes worse due to the non-hardening portion.
(2) The UV light spot incident upon the adhesive 31 is broad and has an incident angle of .theta.1. In this case, since a reflection rate of the non-hardening adhesive 31 is different from that of the V-groove substrate 24, the UV light incident upon the optical fiber array 21 having an incident angle of .theta.1 is reflected, and thus the UV light is not introduced into the adhesive 31. Therefore, the adhesive is not uniformly hardened as shown in FIG. 10b. In addition, a reliability of the optical fiber array 21 becomes worse due to the nonuniform hardening.
(3) Since the adhesive 31 shrinks, the bottom portion of the concave portion of the V-groove substrate 24 is distorted and thus the V-grooves 23 are also distorted. Accordingly, the optical fibers 22 arranged in the V-grooves 23 are moved, and thus a light transmitting loss when connecting is increased. In addition, since a stress due to the distortion is liable to be concentrated to a corner of the concave portion, the V-groove substrate 24 is liable to be fractured from this corner as shown in FIG. 10c.
(4) Since the adhesive 31 arranged between the inner side surface of the V-groove substrate 24 which constructs the concave portion and the outer side surface of the fiber fix substrate 25 is extended vertically, an area of the adhesive 31 contributed to the adhesion is small. Therefore, a connection strength between the V-groove substrate 24 and the fiber fix substrate 25 is decreased.
(5) When the fiber fix substrate 25 is installed with the V-groove substrate 24, it is difficult to insert the fiber fix substrate 25 into the concave portion of the V-groove substrate 24.